In a large skillet, cook bacon over low heat until crisp. Remove bacon and set aside to drain. Add onion, celery, and sage to the bacon fat rendered in the skillet, and cook until onions are translucent and celery is soft, about 3 to 5 minutes. Add sage and broken-up bread to the skillet. Stir in parsley, butter, oysters, salt, and pepper. Lightly toss stuffing, but mix well, and let cool.
Preheat an oven to 400 degrees F.
Butterfly the turkey breast with smooth side down and stuff, folding edges over to hold stuffing. (You may want to secure with skewers or cotton kitchen twine.) Season turkey breast with salt and pepper and place into the oven to roast until it reaches an internal temperature of about 160 degrees F on an instant-read thermometer, about 1 1/2 to 2 hours.
While turkey is in oven, place the turkey neck and giblets in a medium saucepan with 4 cups water and cook until you have about 1 cup of giblet stock. Reserve the neck and giblets, removing meat from neck when cool enough to handle and chopping giblets. When turkey is done, remove breast to a platter to let rest for 20 minutes before slicing. Skim most of the fat from the pan juices, reserving 1/3 cup of the fat. Add the wine to the remaining pan juices and cook over medium high heat until reduced by half. In a separate saucepan, heat reserved 1/3 cup of fat and whisk in flour over moderately low heat for a few minutes to make a roux. Add stock and wine reduction, continuing to cook until gravy simmers. Add reserved cooked and chopped giblets and neck meat. Slice turkey to reveal stuffed interior and arrange on plate. Serve with gravy.